The invention relates to emergency airway devices and emergency thoracostomy devices; more particularly, it relates to trocar devices and method and apparatus for a establishing and maintaining an emergency opening to a body cavity.
Cricothyrotomy
A cricothyrotomy is an emergency procedure performed on a choking person to admit air into the lungs via an opening made in the cricothyroid membrane. The cricothyroid membrane lies between the cricoid and thyroid cartilages of the voice box and is easily located by palpation of the larynx and trachea. Only the thin skin of the throat covers the membrane; no large blood vessels, glands, or other critical structures are normally encountered if this site is used. Though this area is not well-suited to long-term, auxiliary airway maintenance, it offers the safest and most direct access in times of emergency. Presently available devices and methods for performing an emergency cricothyrotomy, however, have serious drawbacks for inexperienced personnel and are of limited effectiveness.
A tracheotomy is a surgical procedure used to admit air into the lungs when the normal breathing passage is obstructed or otherwise ceases to function properly. Briefly stated, a tracheotomy usually involves an incision through the skin of the neck below the level of the voice box and careful manipulation of the thyroid gland and several large blood vessels to expose the trachea. A small circular opening is made in the trachea and an endotracheal tube is inserted to maintain the opening and provide an airway. A tracheotomy is the procedure of choice when an auxiliary airway is to be maintained for an extended period. It is a delicate operation requiring the skill and knowledge of a surgeon and the facilities of a hospital emergency room. Unfortunately, the services of a surgeon and hospital facilities are usually not immediately available to someone who is choking. Unless the patient is given means to breathe, he will die in approximately three minutes. There are well-established non-surgical techniques for removing a supralaryngeal airway obstruction which should be utilized, whenever possible, before any surgical technique is applied. However, these non-surgical methods have a limited range of applicability and are sometimes ineffective. Therefore, there is a need for a device which will enable a person with limited training to provide an emergency airway at any location where a choking emergency occurs.
The inventor earlier created a class of emergency retractable trocar devices to address some of the above concerns, and they are described in U.S. Pat. No. 4,291,690 issued Sep. 29, 1981. However, at the time of the earlier invention, some of the requirements for a practicable, minimally traumatic and fully controllable cricothyrotomy airway were not addressed or dealt with.
Firstly, it is now appreciated that placement of a large trocar (7-8 mm O.D.) through the skin into the trachea is extremely difficult if an adequate surgical incision and sharp dissection of the underlying tissue layers is not accomplished prior to insertion. Extensive testing of many cutting tip and blade designs demonstrates that any blade that is no wider than the inside diameter of the cannula mounted on the trocar shaft and that is merely pushed straight in without any substantial lateral motion will not make an incision that is wide enough to allow a short, straight cannula to be pushed into the upper tracheal airway without excessive force and without extreme danger of over penetration and subsequent crushing trauma to underlying tissues, no matter what the shape or length of the blade. Trauma to the larynx during cricothyrotomy is the primary cause of subglottic stenosis, the most common but preventable complication.
In addition, uncontrolled lateral motion of a blade during incision into the cricothyroid ligament space can cut the recurrent laryngeal nerve resulting in vocal cord paralysis, another major complication of poorly done cricothyrotomy. If a scalpel is used to make a stab incision into the airway, it must be subsequently removed and some type of retractor or tissue separator inserted to enable placement of an airway. When the blade is taken out, the various tissue layers are free to slip relative to one and the path of insertion into the airway can be lost. Re-establishment of the path of insertion can be traumatic and time consuming if not impossible without re-incision.
Secondly, a fixed blade on the end of a trocar can lacerate or penetrate the posterior tracheal wall and esophagus during insertion. This is a potentially fatal complication.
Thirdly, full control of the airway and the ability to forcefully ventilate the patient requires placement of an adequately sized cuffed tracheotomy tube.
What is needed is an improved trocar device to address these additional requirements and any other concerns that arise in such emergency situations.
Thoracostomy
Trauma is the third leading cause of death in the United States and the leading cause of death in young people. Blunt and penetrating chest injuries account for a large number of trauma related deaths. A tension pneumothorax is one of the leading causes of death from chest trauma. A tension pneumothorax occurs when a patient suffers chest injuries resulting in a tear of the lung. Air escapes and builds up under tension outside of the lung in the pleural space. The air under tension changes the dynamics of the circulatory system by impeding blood return to the heart, resulting in severe shock and death if not immediately corrected. This can occur during positive pressure ventilation, when diseased lungs rupture more frequently, following direct chest trauma secondary to fractured ribs. A tension pneumothorax often develops rapidly after the lung injury and therefore the treatment of the tension pneumothorax is an important part of most emergency training protocols.
When a patient develops a tension pneumothorax there is an emergent need to decompress the thorax. When a tension pneumothorax is suspected, a procedure known as needle thoracostomy is typically performed to release the tension. A needle thoracostomy utilizes a large needle or an IV catheter with a one-way flutter valve. The needle is thrust blindly through the anterior chest to decompress the pneumothorax emergently. This procedure, sometimes referred to as xe2x80x9cplacing a flutter valvexe2x80x9d, is routinely taught to physicians, nurses and paramedics during formal training, including the Advanced Trauma Life Support (ATLS) and Advanced Cardiac Life Support Courses (ACLS), courses given to most practitioners dealing with critically ill patients.
Although generally helpful, there are several drawbacks to the current needle thoracostomy procedure. The needle or IV catheter can easily lacerate the lung and produce further lung injury or hemothorax (bleeding into the chest). In fact, a chest tube must always be placed after a needle thoracostomy to treat the presumed needle injury from the procedure, even if the diagnosis of pneumothorax was incorrect! Most injuries to the lung produce some degree of hemothorax anyway, and that increases the chance that blood will clog the typically small caliber needle that is currently used. Today, most health care providers simply use an IV catheter or make-shift needles with balloons, finger cots, or slit finger tips of latex gloves on the end to decompress a tension pneumothorax.
In a typical scenario, a trauma patient with an injured lung develops profound shock after endotracheal intubation. This results because the air introduced under positive pressure escapes through the injured lung and a tension pneumothorax ensues. The paramedics would listen for decreased breath sounds, and if absent, would perform a needle thoracostomy by placing a needle or IV catheter through the side with the decreased breath sounds.
Another common scenario is the patient in extremis who fails to respond to resuscitation. As called for in the ATLS and ACLS protocols, needle thoracostomies are often performed to xe2x80x9crule outxe2x80x9d a tension pneumothorax. While this can be successful when a tension pneumothorax is actually present, many patients are not completely decompressed because either the needle does not stay in position, the needle is too small in caliber to adequately decompress the thorax, or the needle has become clogged with blood and cannot continue to function.
In other situations, patients arrive at hospital with a clogged xe2x80x9cflutter valvexe2x80x9d, or it has become ineffective because of the variable thickness of the chest wall, or it has fallen out or become displaced in transport. When this happens, a tension pneumothorax redevelops, suggesting at least that the current technology is inadequate.
A review of the medical literature reveals several reports of attempts to develop a device in the 1970""s. The McSwain Dart is reported as a device that utilized a larger catheter and a tapered steel needle to decompress tension pneumothoracies. Despite an initial series of reports of the benefits by Dr. McSwain (see McSwain, JACEP 1977; 6(7):325-5; McSwain, Med. Instrum. 1982; 16(5);249-50; and Wayne, Ann. Surg., 1980; 191(6):760-2), the device does not appear to have caught on and does not appear to be currently in use. Independent critical review of the product criticized it as being dangerous because of the large steel needle""s propensity to lacerate the lung.
The issue of the needles becoming dislodged deserves further discussion. Patients with tension pneumothoracies often have multiple injuries and are very ill. There is a lot going on in an attempt to resuscitate them, sometimes including cardiopulmonary resuscitation (CPR). An unsecured needle or IV catheter can easily fall out and be unnoticed in this situation. Furthermore, long transport times are common as patients are often transferred great distances to regional trauma centers for specialized care. If the needle is dislodged or becomes clogged with blood, air begins to build up in the chest under tension. Frequently, upon arrival at an emergency room and when a large bore chest tube is placed, a large gush of air is encountered, indicating that there was a large volume of air not released by the needle thoracostomy.
This background taken together suggests that, while needle thoracostomy may be immediately life saving, it often works only briefly and it involves multiple risks. The pathophysiology of a tension pneumothorax can reoccur and the patient can again deteriorate. While it is ideal to quickly place a large bore chest tube after a needle thoracostomy, this is not practical during long ambulance or airlift transports or when the patient is in the immediate care of health care providers who do not routinely place chest tubes.
In any event, the literature suggests that there are far more indications for chest tube insertion, such as in pneumothoracies, hemothoracies, pleural effusions and empyemas, than there are for emergent needle thoracostomy. As previously mentioned, placement of a chest tube is always recommended after a needle thoracostomy anyway because of potential hemothorax.
Non-retractable trocar chest tube insertion systems are also known. These are also generally considered dangerous and, although purchased by many hospitals, not often used by physicians. They involve the use of a hollow sharp metal trocar with a chest tube inside. After the skin is incised, the trocar is advanced through the lateral chest wall until the pleura is penetrated and the chest tube is advanced forward while the trocar is withdrawn. The danger lies in having a sharp pointed, non-retractable trocar in the chest where it can injure the lung or heart. Because this technique is considered dangerous, most surgeons employ the standard hemostat technique of chest tube insertion. This involves incising the lateral chest wall, dissecting a subcutaneous tunnel above the rib with the finger and instruments, and punching through into the pleural space. A tube is then grasped with a hemostat and inserted through this tunnel. Sutures are then used to close the large wound around the tube.
A novel retractable trocar thoracostomy system is needed to replace the current needle thoracostomy technique that is used in emergency situations for patients who have tension pneumothorax, and to replace current chest tube insertion devices and procedures, as described above. A retractable trocar should be quicker, easier and less traumatic than currently used techniques, provided, among other criteria, that the cutting mechanism used to enter the chest is designed not to injure deep structures.
Devices and methods disclosed herein solve both the cricothyrotomy and the thoracostomy problems discussed above by, among other things, incorporating a twin-bladed, retractable incision mechanism, mounted within the end of a trocar. That is, not only is the trocar retractable, but the two part blades themselves are retractable within each trocar. Such devices make a precise incision greater than the width of the included cannula that is delivered with the trocar, and preferably about twice as wide as the I.D. of the cannula.
A surgical cutting tool is disclosed. It has a xe2x80x9ccam actionxe2x80x9d (the term defined further herein) retractable blade assembly with two blades, each with a blade edge and an angled blade point. Preferably, the blade assembly has two substantially identical blades each having an edge face with a single bevel cutting edge disposed at an angle to a longitudinal axis of the blade, each edge ending in a blade point at a distal end of the blade, each blade further having a pivot pin hole in a proximal region of the blade with a hole center lying on the blade axis. Also each blade has a cam slot distal to the pin hole with an distal cam slot center lying substantially on the blade axis and a proximal cam slot center lying substantially on a line between the pin hole center and the blade point. The two blades are pivotally mounted edge face to edge face upon the pivot pin engaged within both pin holes. The tool also has a cam pin, the cam pin relatively stationarily engaged (see below) within both cam slots, so that movement of the pivot pin in a distal direction urges the two blades to rotate their two blade points closer to each other in an extended configuration, and movement of the pivot pin in a proximal direction urges the two blades to rotate their two blade points further from each other in a closed or retracted configuration.
In the extended configuration, the two blades have overlapping blade points to form an extended blade profile, and the profile preferably has a relatively less sharp, xe2x80x9csafe zonexe2x80x9d (discussed further below) at its tip. The tool also has a spring and a pushrod engaging the blades to extend the blade assembly against spring resistance into a locked position when fully extended; the pushrod may advantageously be a wire, or other longitudinally flexible, but compression and stretch resistant, push-pull type linkage such as wire wound cable.
A improved cannula for surgical procedures is also provided. It is a self retaining cannula with a collapsible retention lattice at a distal end. In one aspect, the lattice is further comprised of struts, and the struts are formed in a partial frusto-conical (truncated cone shape) configuration at the distal end of the cannula. In another aspect, prior to assembly, the lattice structure is formed substantially flat, and the cannula is segmented, with cannula segments depending radially from the flat formed lattice. Alternatively, the cannula and lattice structure, after assembly, has four contiguous rectilinear zones defined by an intersecting pair of substantially perpendicular lines, a central portion of each of which is open or latticed.
A retractable trocar device is provided for placing and maintaining a percutaneous tube into a body cavity such as an airway or a chest cavity. The device has a cam action retractable blade assembly with two blades, each with its own blade edge and angled blade point. The blade assembly has two substantially identical blades each having an edge face with a single bevel cutting edge disposed at an angle to a longitudinal axis of the blade, each edge ending in a blade point at a distal end of the blade, the two blades pivotally mounted edge face to edge face upon a pivot pin, with the blade points overlapped in an extended configuration. The blade assembly of the trocar device desirably also has a xe2x80x9csafe zonexe2x80x9d at a tip of the extended configuration, as discussed above.
The trocar device has a handle enclosing at least a portion of a spring and a pushrod, with pushrod under spring tension or compression in an extended configuration, the pushrod engaging the blades to extend the blade assembly against spring resistance into a locked position when fully extended. There is also provided a releasable lock mechanism for the pushrod. Some embodiments of the trocar device have an additional tapered zone proximal to a distal end of a trocar shaft within which slides the pushrod. The trocar device has either a self retaining tubular cannula engaged for delivery upon a trocar shaft, or a self retaining expandable cannula folded and engaged upon a trocar shaft. There is also provided an optional self deploying, removable, one way exit valve foldably engaged upon a hub end of the cannula.
The cannula may alternatively be a multi-segmental flexible piece, the segments joined in the center by a geometrically regular network of filaments, the filaments shaped and conjoined in such a way as to enable the segments to be folded and interengaged into a substantially tubular shape with the filaments thereby forming an outwardly collapsible structure having at least two break lines. With this in mind, other geometrical arrangements will occur to those skilled in the art.
The inventor developed an earlier retractable trocar device that is described in U.S. Pat. No. 4,291,690 issued Sep. 29, 1981, and by this reference the text and drawings of this patent are herewith incorporated as if fully set forth herein.
The incision mechanism for an embodiment of the invention directed particularly toward cricothyrotomy has two identical single beveled blades that are pivotally mounted for cam action expansion with their cutting edge sides face to face and overlapped at their respective points when fully extended. They form a single pointed delta or xe2x80x9cVxe2x80x9d shaped edge when extended, with (looking edge on) one half beveled on the left and the other half beveled on the right, so that there is a double thickness, double beveled point in the center generally having a blade sharpness angle that is twice that of either single blade. The preferred profile of this delta cutting edge is about 100xc2x0 because it is desirable to make as gentle a surgical incision and insertion as possible to avoid crushing trauma to the larynx, without using so sharp and long a point that there is any danger of penetration of the tracheal wall at full insertion. The size and generally cylindrical shape of the tracheal lumen also make it further desirable that the lateral-most points of such a cutting edge come to rest (at furthest insertion) at the widest point of the lumen, so to avoid lacerating the tracheal wall during incision. It has been found that a delta point of about 100xc2x0 optimizes and addresses these concerns most favorably by presenting a relatively pointed and sharp edge for ease of incision, while maintaining a relatively short point length with lateral point spread no wider than a typical tracheal lumen.
In this embodiment, the trocar system or set is pushed straight into the cricothyroid ligament space at a right angle to the surface of the skin. Flutes extend through the length of the trocar and as soon as the airway is entered, a hissing sound can be heard indicating full penetration into the airway. At this point the index finger is moved to conveniently compress a trigger mechanism that releases a spring activated retractor which closes the blade mechanism and pulls it back into the trocar, thus producing a relatively blunt end. The tapered conical end of the trocar, upon which is preferably mounted a short 7.2 mm I.D. self-retaining, expandable airway cannula, centers the trocar within the cricothyroid ligament space and gently dilates the incision as the trocar is easily, controllably inserted.
In order to prevent over penetration during initial insertion if excessive force is used or the patient lurches suddenly, two penetration control bars extend down from the sides of the handle. The bars come to rest against the surface of the throat and effectively stop the advance of the blade. They are pulled back automatically into the handle as the spring-activated retractor pulls back the blades to allow complete insertion of the trocar.
It is desirable that the blade mechanism be closed prior to withdrawing the shaft from within the cannula. When this is not done, the outwardly extended blades can potentially jam and damage the cannula. In order to eliminate this possibility, a safety switch has been designed in that automatically sets off the spring-activated retractor if the operator tries to pull the shaft from the cannula but forgets to retract the blades first.
After the blades and penetration control bars have been retracted, the trocar is inserted fully, seating the hub of the airway cannula against the throat. At this point the trocar shaft is pulled out as tabs on the hub of the cannula are held against the throat. This action causes the end of the cannula, which is snapped into four retentive grooves on the end of the trocar shaft, to flare outwardly as the shaft is withdrawn, thus anchoring the preferably self retaining airway. The light finger spring action of the expanded plastic struts prevents expulsion of the tube as the patient forcefully exhales.
In order to fulfill the requirement that an adequately sized cuffed tracheotomy tube can be placed, the cannula is made so that its preferably thin walled quadrisegmental tube will dilate as the cuffed tube is pushed easily through it into the trachea.
The preferred tracheal cannula is preferably made of polypropylene. It is preferably molded in a relatively flat plane with the ends of the quadrisections joined in the center to a network of interconnecting struts or filaments that is stretched and folded up to form a basket weave-like pattern as the sections come together, overlapping like the petals of tulip, to form the percutaneous tube. The extracorporeal portion of the cannula comes together to form the manipulative tabs on the hub, leaving the cannula segments to form a long tapered, funnel-like throat whose inner surfaces wedge outwardly as the cuffed tube is pushed in. A short cylindrical xe2x80x9ckeeperxe2x80x9d, which fits over the assembled sections of the funnel to hold the cannula together, is preferably provided and shaped as a standard 15 mm resuscitator coupling. If placement of a cuffed tube is indicated, the keeper is removed to allow insertion and expansion of the cannula.
This device, described above for use in performing cricothyrotomy, may, with scale and relative dimensions modified, also be used for performing a thoracostomy.
A thoracostomy system is also disclosed that utilizes a large bore retractable trocar instead of a needle to decompress the thorax, with the trocar placed anteriorly, similar in location to current needle thoracostomies. This emergent decompressive thoracostomy trocar preferably includes a one-way valve so air could exit, but not enter the chest. In one embodiment there is provided a thin, flat elastic membranous sleeve preferably attached to the inside of the extracorporeal hub of the cannula, and which is inserted into the cannula during assembly of the device by insertion of the shaft into the cannula, thereafter to turn inside out with withdrawal of the shaft to make a one-way flutter valve. Where deemed medically appropriate, this system can also be attached to an air drainage system for definitive care of an isolated pneumothorax.
Preferably, a safe-ended incision mechanism is provided that is retracted upon entering the chest, thus avoiding the potential for internal injury during deployment. The incision mechanism for this embodiment of the invention directed particularly toward thoracostomy also has two identical single beveled blades that are pivotally mounted for cam action expansion with their cutting edge sides face to face and overlapped at their respective points when fully extended. They also form a delta or xe2x80x9cVxe2x80x9d shaped edge when extended, with (looking edge on) one halfbeveled on the left and the other half beveled on the right, so that there is a double thickness, double beveled point in the center generally having ablade sharpness angle that is twice that of either single blade.
The preferred profile of this alternate cutting edge is about a 135xc2x0 delta shape with a small zone, preferably about 1 mm, at the double thickness, double beveled center of the delta edge. The edge of this small zone is preferably perpendicular to the long axis of the trocar shaft. This slower cutting, less pointed zone is generally the result of an additional grinding step on each blade point that takes off a tiny portion of each sharp blade tip, while leaving the newly ground tip at the same blade sharpness angle as the rest of the blade, but in a new plane slightly skewed with respect to the plane of the cutting edge, and are the preferred safe-ended mechanism referred to above. The shallower delta shape and this safe zone serve to limit the depth and danger of initial penetration, particularly with respect to the danger of damage to underlying internal organs. The rib cage is strong enough to sustain the forces necessary to incise the dense, relatively noncompliant intercostal tissues fixed between the ribs, and to dilate a chest tube channel with this relatively wider, less pointed, slower cutting edge. These intercostal tissues provide sufficient resistance to allow the necessary cleavage forces to be achieved and maintained during sharp dissection.
On the other hand, the highly compliant, soft, rubbery tissues of the underlying internal organs do not provide sufficient resistance (as does the rib cage) to the widely spread axial pressure of the plunging trocar to enable it to penetrate. Preferably, the thick tapered body of the trocar shaft starts only 5 mm behind the leading edge of the extended blade, further adding to the resistance to penetration of soft organs. In addition, this style point prevents accidental engagement and distortion of the blade tip by the superior border of the rib (in case it is bumped) during insertion.
Flattening the V shaped incising edge to about 135xc2x0 spreads the force of insertion over a wider area and increases the amount of pressure that is needed to start penetration. Since the apex of the blade point is thus closer to the plane of the lateral blade ends, the blade point has to penetrate only about 5 mm to make a complete incision into the chest cavity. In this short distance, the soft underlying internal organs cannot produce enough resistance to the slower cutting delta edge to be punctured or cut. Significantly, the expanded or extended blade mechanism is closed and spring retracted into the trocar shaft at this point by the simple push of a button on the handle of the insertion tool and, as is also true of the cricothyrotomy device disclosed above, the trocar has a relatively blunt end throughout the rest of the insertion sequence.
The trocar is then fully inserted and then the trocar shaft is removed to leave in place an included 13 to 14 mm I.D. plastic delivery cannula. The cannula can then manually be directed to the portion of the chest where the chest tube needs to be inserted. The chest tube is then inserted through the cannula, and the cannula is removed (such as by the Seldinger Technique). The chest tube can then be hooked up to closed system drainage, if further deemed necessary. In situations when pleural adhesions are expected however, the hemostat technique can still be used if ultrasound equipment is not available to identify the exact location of the intrathoracic bolus of air or blood.
There are several advantages to the system presented herein. 1) Retractable trocars in general have shown themselves to be relatively safe in laparoscopic surgery and are therefore likely to be safer than the known system of plunging a large, nonretractable needle blindly into the chest. 2) There are no needles involved; this should appeal in emergency situations where high risk accidental skinbreak exposures often occur. 3) The caliber of the related cannula is much larger than any needle, and therefore less prone to clogging with blood. 4) A novel self retaining cannula is preferably employed, successfully addressing the problem of needle displacement. 5) The one-way valve does not allow air to enter from outside the chest, which is advantageous in the non-intubated patient or when the diagnosis of a tension pneumothorax is after all incorrect.
In the disclosed system the smallest possible surgical lesion is produced in the process of applying any of the devices disclosed, resulting in less post-operative pain and faster healing; the chest tube can be placed with the fewest possible steps in the shortest possible time; and the incision produced will be just large enough to allow relatively easy placement through the incised tissue of a preferred 13-14 mm I.D. delivery cannula that is sized to facilitate installation of a 36 size French chest tube.
In addition, the relatively minimal size of the incision and the dilation of the incision channel by a preferably tapered trocar shaft retains natural tissue resiliency and causes the tissue to close tightly and directly appose the chest tube after the delivery cannula is withdrawn. This allows a negative intra-thoracic pressure to be reliably maintained without the need for sutures on either side of the chest tube to close gaps around it. An optional one way exit valve can be included as a removable attachment for the delivery cannula which makes it useful for reducing compression pneumothoracies and eliminates the need to perform a secondary thoracostomy after the standard needle puncture technique. If the location of the chest access needs to be changed, the trocar can be easily reassembled and reapplied.
Installation of the preferred self-retaining delivery cannula in a single stroke prevents the path of insertion into the chest cavity from being lost during the procedure. The end of the thin-walled cannula collapses and flares out as the blunted trocar shaft is pulled from within it. This anchors the cannula lightly within the chest cavity. A conventional chest tube can then be placed through it with no further manipulation of the tissues, whereas the conventional technique requires multiple penetrations and extensive tissue manipulation to insert the tube.
The differences between the very restrictive anatomy of the laryngeal hard structures and the vacuous depths of the chest cavity will allow a thoracostomy trocar to be inserted further during deployment, provided that the end can be made safe after initial penetration. Thus one alternate embodiment adds a tapered extension of the trocar shaft just behind a relatively smaller set of blades, the tapered extension progressively dilating the smaller resulting incision and thus causing the tissues to fit more tightly around the cannula and result in a smaller scar. This version has a preferred 13 mm shaft which tapers slowly down to 9 mm and has two 9 mm blades (rather than the preferred 13 mm blades of the other version). A self-retaining 13 mm I.D. delivery cannula is provided to fit it on either version, depending on how the collapsing struts on the end are unfolded after it is made.
There is a potentially large market for this system, as it could be used by paramedics, emergency physicians, trauma surgeons, ICU doctors and anesthesiologists, all of whom encounter patients with pneumothoracies. Furthermore, a device such as this would improve the comfort and safety of critically ill patients during air transport because the attendant changes in altitude are known to worsen the physiologic effects of pneumothoracies by changing the air pressure differential in the thorax. The product of the invention can even be stocked on the xe2x80x9ccodexe2x80x9d carts or with other emergency equipment and therefore be immediately available. Code carts, used for emergency resuscitations in hospitals, are found in every patient care area, emergency room and operating rooms in every hospital as well as in many clinics. This product could easily be included with emergency equipment carried by paramedics and flight crews that care for injured patients prior to arrival to a hospital.
It will be appreciated that placement of a large ( greater than 10 mm O.D.) trocar through the skin into a body cavity (trachea, thorax, abdomen) is extremely difficult, if not impossible, if an adequate surgical incision and sharp dissection of the underlying tissue layers is not accomplished prior to insertion. Extensive testing of many cutting tip and blade designs demonstrates that any blade that is no wider than the inside diameter of the cannula mounted on the trocar shaft and that is merely pushed straight in without any substantial lateral motion will not make an incision that is wide enough to allow a short, straight cannula to be pushed through the body wall without excessive force and without extreme danger of over penetration and mutilation of underlying tissues, no matter what the shape or length of the blade. In addition, any uncontrolled lateral motion of a pointed blade during incision into the body cavity can lacerate organs which may be immediately underlying. The retractable cutting mechanism disclosed herein, that preferably makes an incision about twice as wide as the trocar shaft itself, enables easy and reliable insertion of the trocar.
As discussed above, the skin and body wall are well designed to resist puncture and penetration into body cavities. Only with adequate sharp surgical incision of the skin and underlying tissues can insertion of a large bore (10 mm+) percutaneous tube be easily, safely and reliably accomplished. Gentle, progressive dilation of the incision is desirable for installation of the tube. The disclosed design accomplishes incision, dilation and installation in one motion, one step, with one instrument, with anchoring and gentle retention of the preferred inserter sleeve/breathing tube/one-way valve combination accomplished as the shaft is withdrawn from within the cannula.
The tapered dilator segment of the trocar shaft is self-centering and insures axial force application during insertion, to prevent unwanted lateral motion and to prevent inadvertent deep organ penetration. A preferably built in tapered wound dilator, provided in varying sizes, transfers dilating forces from the tip of the trocar shaft to the sides of the cannula struts, due at least in part to preferred inletting of the collapsible cannula struts onto the trocar shaft. The resulting configuration locks the cannula onto the shaft and enables out folding of the self-retaining mechanism during withdrawal of the shaft.
For other applications, the retractable twin-bladed incision mechanism can be made in a large or miniature scale and can also be used to deliver tubes that are not expandable or are not self-retaining. The preferred spring loaded rod linkage which extends and retracts the blades can be made to any desired length and can be both flexible and activated remotely, as through a surgical endoscope or catheter. Therefore, without departing from the scope of the invention, the device could be modified by those skilled in the art for endoscopic microsurgical insertion of tubes or shunts which require a precise, controlled puncture into a body cavity.